Pocket springs explained: coils, gauge, zones and edges

The short answer: In a pocket-spring unit, every coil is sewn into its own fabric pocket, so each one compresses separately from its neighbours. That lets the mattress follow the shape of your body more closely and keeps a partner’s movement from travelling across the bed — the two big advantages over older designs where the coils are wired together. On a spec sheet, spring count only means something when compared at the same size, a lower wire gauge number means a thicker, firmer wire, zoning means firmer springs where the body is heaviest, and a reinforced edge keeps the perimeter usable.

Three kinds of spring unit

Type	How it is built	Feel	Partner movement
Bonnell	Hourglass-shaped coils joined by spiral wires	Firm, springy, uniform	Travels across the bed
Continuous coil	Rows formed from one long length of wire	Firm and even	Travels across the bed
Pocket springs	Each coil sewn into its own fabric pocket; pockets glued or joined together	Contours to the body	Mostly absorbed

Bonnell units are the traditional innerspring: durable and inexpensive, but because every coil is tied to its neighbours, pressing on one pulls on the others. Continuous coil units are similar in that respect. Pocket springs cost more to make but behave quite differently, which is why almost every hybrid mattress uses them.

Spring count

Spring counts appear on many spec sheets, and more springs generally means finer contouring, because each coil is smaller and responds to a smaller area of the body. But counts are only comparable at the same mattress size — a count quoted for a King cannot be set against one quoted for a Queen — and brands do not always say which size they mean. Beyond a certain point, extra springs make less difference than the quality of the coils and the comfort layers above them.

Wire gauge

Gauge is the thickness of the steel wire, and the numbering runs backwards: a lower gauge number means a thicker wire. A 13-gauge coil is thicker and firmer than a 15-gauge one. Thicker wire generally feels firmer and is often more durable; thinner wire feels softer and more responsive. Many units mix gauges — thicker wire around the edge, or in zones that carry more weight.

Zoning

A zoned unit varies the springs along the length of the mattress, usually with firmer support under the hips and softer give under the shoulders. That helps keep the spine in line, particularly for side sleepers, whose shoulders need to sink further than their waist. Zones are created with different wire gauges, coil heights or pocket arrangements.

The number of zones is not a score. A well-designed three- or five-zone unit can support better than a poorly designed seven-zone one, and the comfort layers above the springs still decide much of what you feel. Our sleeping position guide explains why zoning matters for each position.

Edge support

The perimeter of any mattress compresses more than the middle, because there is nothing beside it to share the load. Pocket-spring units handle this in two main ways:

• A row of firmer edge coils — thicker wire or a different coil around the outside.
• A foam encasement — a frame of dense foam surrounding the spring unit.

Good edge support makes more of the mattress usable, helps when you sit on the side of the bed, and stops the feeling of rolling off. It matters most for couples, who use more of the width — see choosing a mattress for two.

What sits on top

Springs provide support; the comfort layers above them decide the feel.

• Foam or memory foam layers add cushioning and contouring.
• Latex adds buoyancy and helps the mattress sleep cooler. See latex explained.
• Micro-coils or mini pocket springs are a layer of small coils within the comfort system, adding airflow and bounce.
• Pillow tops and euro tops are extra padded layers sewn onto the top surface.

Two hybrids with similar spring units can feel completely different because of what is above them. Our hybrid vs memory foam guide explains how to weigh the layers.

Noise and durability

A new pocket-spring mattress is very quiet: the fabric pockets stop coils rubbing against each other. Over many years, coils can begin to creak, but a noisy bed is more often the base than the mattress. Steel springs generally outlast the soft foam above them, so in a hybrid it is usually the comfort layer that wears first.

Questions to ask about a spring unit

• What type of spring unit is it — pocket, Bonnell or continuous?
• How many springs, and in which size is that count quoted?
• What gauge is the wire, and does it vary across the mattress?
• Is it zoned, and how?
• How is the edge reinforced?
• What comfort layers sit above the springs, and how thick are they?

If a product page does not answer these, the brand’s customer service usually can. For what the other layers in a mattress do, see what your mattress is made of.

Our best hybrid and pocket spring mattresses page lists specific models.

Common questions

Are pocket springs better than Bonnell springs?
For most people, yes: they contour better and pass far less movement across the bed. Bonnell units are firmer, cheaper and durable, but noisier and less forgiving.

Does a higher spring count mean a better mattress?
Only up to a point, and only when counts are compared at the same size. Coil quality, gauge and the comfort layers matter as much.

What does a lower gauge mean?
A thicker wire. A lower gauge number is firmer and usually more durable.

Are pocket-spring mattresses good for couples?
Yes. Because each coil moves on its own, a partner’s movement is largely absorbed, and a reinforced edge makes the full width usable.